1. Field of the Invention
The present invention relates to a liquid crystal lens, and more particularly, to a liquid crystal lens having a plurality of concentric electrodes, where a gap between two adjacent outer concentric electrodes is different from a gap between two adjacent inner concentric electrodes.
2. Description of the Prior Art
Liquid crystal (LC) lens technology is one of the most promising technologies exploiting the unique physical and optical properties of liquid crystal materials. Unlike a conventional glass lens, the LC lens can converge or diverge incident light rays according to an electric field applied thereon. In particular, a focal length of the LC lens can be tuned by varying the applied voltage. Since no mechanical motions are needed to adjust the focal length, the LC lens has many advantages over glass lenses and can be used in all types of image capturing techniques.
Please refer to FIG. 1(A). FIG. 1(A) is a diagram illustrating a prior art LC lens structure 100. The LC lens structure 100 includes two glass layers 110 and 120, two ITO (Indium-Tin Oxide) electrode layers 112 and 122 respectively formed on the glass layers 110 and 120, and an LC layer 130. FIG. 1(B) is a top view of the ITO electrode layer 112, where the ITO electrode layer 112 is patterned to have a circular hole. To achieve the lens effect, it is necessary to shape the electric field inside the LC layer 130 similar to a curvature of the glass lens. As illustrated by referring to the electric field shown in FIG. 1(C), however, the LC lens structure 100 does not provide a required shape of the electric field inside the LC layer 130.
To improve the lens effect of the LC lens structure 100, a concentric ring design shown in FIG. 2 is provided. FIG. 2(A) is a diagram illustrating another prior art LC lens structure 200. The LC lens structure 200 includes two glass layers 210 and 220, two ITO electrode layers 212 and 222 respectively formed on the glass layers 210 and 220, and an LC layer 230. FIG. 2(B) is a top view of the ITO electrode layer 212, where the ITO electrode layer 112 is patterned to have concentric rings, and the concentric rings are supplied by different control voltages V1-V3. Although the shape of the electric field inside the LC lens layer 230 shown in FIG. 2(C) is better than that of the LC lens layer 130 shown in FIG. 1(C), design of the LC lens structure 200 is more complicated because more control voltages V1-V3 are needed.